Powered medical devices and/or instruments have been in use for many years. However, one of the major drawbacks of such instruments is the relatively large amount of cables required for operation. For example, cutting devices require the use of a power cable to provide electrical power for the medical instrument. Likewise, video endoscopes have traditionally required the use of a power cable and a data transmission line as well as a fiber optic cable for transmission of illuminating light.
These lines are cumbersome and may even present operational difficulties for the user. For example, these cables can get in the way of other surgical instruments and also make the endoscope top heavy and difficult to maneuver. Additionally, surgeons often complain of fatigue because they are constantly working against the weight of the cables attached to their instruments.
Still another problem that cables present is that they can compromise the procedure if mismanaged as contact with the cables, by another individual or with an object, may suddenly cause tugging on an instrument and/or accidentally cause the instrument to be thrust into or impinge upon delicate tissue. In fact, this problem is so prevalent that many surgeons wrap the cables around their wrists several times to prevent cable forces from transferring directly to their instruments.
Yet another problem faced by current system is the lack of electrical isolation between the patient and the source of electrical power. As medical devices are inserted into a patient's body during a procedure, the patient is a risk of receiving an electrical shock if the device ground faults or shorts. Accordingly, a system that will provide for complete electrical isolation between a patient and the source of electrical power would be advantageous.
In an attempt to address some of the problems associated with “wired” devices, a number of systems have sought to provide “wireless” systems with limited success. For example, systems have provided for wireless transmission of image data from an endoscope to a display and have further provided an energy source positioned on the endoscope. This provides the advantage that the cables are eliminated as the power source on the endoscope powers both the image circuitry and a light source (typically an LED) positioned on the endoscope. However, these systems suffer from a number of drawbacks.
First, battery systems continue to be inherently large, heavy and costly. As was previously stated, physicians that have to manipulate a relatively heavy device or fight against relatively heavy cables, suffer from fatigue, especially in relatively complicated and long surgical procedures.
Another problem with battery-powered systems is that they may not be recharged or they may only be partially recharged, thus causing them to shut down or at the very least, causing the device to function at a non-optimal level (i.e. low voltage level) for a portion of the procedure. While procedures may be put into place to limit mistakes in the recharging process, human-error will result in some devices not being charged or not being fully recharged. It is widely know that it is critical to limit the time that a patient is under general anesthesia. Any delay due to, for example, failure of a medical instrument or even sub-standard operation and delay as a new instrument is obtained, connected and powered up should therefore be avoided if at all possible.
Still another problem with battery-powered systems is that batteries inherently deteriorate over time. For example, initially a battery may provide a sufficient amount of power output to operate a particular medical instrument for a given period. However, as the battery is used and recharged again and again, that power output slowly decreases until the battery can no longer maintain sufficient charge to operate the medical device for the length of the procedure. While the battery may function sufficiently for a certain number of operations, it is unclear if and/or when the battery will fail, for example, during a medical procedure. Regular replacement of batteries can limit this problem, however, this greatly increases the cost associated with using wireless devices. Battery testing can also limit this problem, but this takes time and involves human error if the individual forgets, makes a mistake in testing or misreads the results.
In still another system disclosed in U.S. Patent Application Publication No. 2007/0290814 (Yoshida), a wireless power feeding system is provided for wirelessly transmitting electrical energy to a capsule endoscope system. The system in Yoshida includes an image pickup unit that is swallowed by the individual (i.e. a capsule) and generates and transmits an image signal of the area adjacent to the capsule. The Yoshida system is a capsule that will slowly work its way through the body providing various still frame images of the areas (e.g. gastro-intestinal tract) through which it passes. Yoshida uses an inductive power transfer method that is based on the orientation of the power transmitting coil relative to the power receiving coil. For example, Yoshida states that “the amount of power received by a power receiving coil is maximized when the winding axis of a power transmitting coil substantially matches the winding of the power receiving coil” and that “direction and position of the magnetic member” is “changed to collect more of the magnetic flux.” (Pars. 55-57) Accordingly, the position and orientation of the transmitter and receiver is important to Yoshida to ensure a sufficient amount of energy is transmitted to the capsule. Such a system may be acceptable for use with, for example, a capsule that is not manipulated by a surgeon. However, in an active medical procedure, the surgeon is regularly (if not almost continually) manipulating medical instruments (e.g. cutting tools, video endoscopes, etc.) as necessary to accomplish the procedure. Therefore, the system taught in Yoshida could not be used for an active medical procedure as the power transmitting coil would not regularly be aligned with the receiving coil. It would be virtually impossible for the surgeon to perform the procedure if the surgeon had to maintain the tool in alignment with the power transmitter as the surgeon needs to freely move the tool without regard to external issues. In any event, the capsule system is certainly not designed for manipulation by the physician (i.e. it is designed to be ingested by the patient).
Another limitation of the system taught in Yoshida, is that it is not provided to transmit a video stream of information that requires 30-60 frames of information per second. Rather, the system taught in Yoshida is a passive system that provides still frame images as it passes through the body. (Pars. 24-25) In fact, in view of the limited amount of power that can be transmitted to the capsule, it is questionable whether the video could provide a video stream of the area it is slowly passing through. Additionally, the system taught in Yoshida does not provide for the constant light output needed for continual illumination for video transmission. The power requirement to perform this functionality is orders of magnitude higher than is contemplated in the Yoshida system.